1. Field of the Invention
The present invention relates generally to additives for lubricating oils used in internal combustion engines, and to lubricating compositions containing such additives.
The additives of the invention combine dispersancy with viscosity index improving. That is to say, they improve the viscosity properties of a lubricant by lessening its tendency to change viscosity as the temperature changes and, at the same time, disperse and maintain suspended sludge, varnish and the like which form in the lubricant during use.
2. Description of the Prior Art
The prior art to which this invention relates is aware of the following U.S. Pat. Nos. 3,789,980 3,687,849; 3,879,304 and 3,076,791. The first of these discloses a lubricating oil additive consisting of the reaction product of a primary or secondary amine, and a hydroperoxidized ethylene/propylene copolymer; U.S. Pat. No. 3,687,849 describes lubricant additives consisting of graft polymers prepared from various polymerizable unsaturated monomers and an oxidized degraded interpolymer of ethylene and propylene. U.S. Pat. No. 3,879,304 reports a terpolymer having thereon a graft of a polymethacrylate. U.S. Pat. No. 3,076,791 discloses lubricating oil additives produced by the free radical reaction of an ethylene/propylene copolymer with an amine.